Guayadeque includes a projectM music visualizer (experimental).
Open it with View -> Visualizer or (F9): it shows a dockable panel that can also float. Pressing F9 again hides it.
View -> Visualizer Full Screen (Shift+F9) opens it in a dedicated fullscreen window from any state; a second press, Esc, double-click or "Exit fullscreen" in the right-click menu docks it back, while F9 from the fullscreen window closes it and hides the panel. Both shortcuts are configurable in Preferences -> Shortcuts.
While music plays, the playback pipeline feeds real audio to the visualizer (synthetic audio is used while nothing plays). Presets play in shuffle mode with automatic switching; the canvas context menu offers next/previous preset, fullscreen and close.
A subset of 50 projectM presets is shipped with Guayadeque, so the visualizer works out of the box. It builds against libprojectM 4, 3 and 2.1 (v4 preferred when several exist). Its options live in Preferences -> Visualizer.
The visualizer needs an X11 display. On Wayland sessions without X11 it is unavailable and its menu entries stay disabled; run Guayadeque with env GDK_BACKEND=x11 guayadeque (XWayland) to use it there. We won't force XWayland in the .desktop so as not to degrade the whole app on Wayland (scaling/integration) or break sessions without XWayland.
Native Wayland support waits for a newer wxWidgets with EGL canvas support (wx 3.4).